1. Field of the Invention
The present invention relates to gas measurement. More particularly, the present invention relates to gas measurement of methane emissions of an internal combustion engine. More particularly, the present invention relates to methane sensors that are utilized so as to provide an indication of excess methane emissions from an internal combustion engine.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Although most automobile, truck and industrial engines are operated on gasoline or diesel fuel, natural gas is recognized as a potential fuel for such engines because it is viewed as a “clean” fuel. Natural gas comprises mostly methane (CH4). It has been found that engines operate with methane or natural gas as a fuel produce lower amounts of carbon monoxide, carbon dioxide and unburned hydrocarbons of the type that contribute to smog than engines operated on gasoline. The lower quantity of such hydrocarbon emissions is seen as particularly beneficial because of the corresponding reduction in the formation of ground level ozone. The reduction in carbon dioxide is also beneficial because carbon dioxide is a greenhouse effect gas. Since gasoline and natural gas are both hydrocarbon fuels, it would seem that operating practices and exhaust treatment techniques developed for gasoline engines would be directly applicable to methane-fueled engines. However, such is not the case.
During the past, noble metal catalysts supported on high surface area alumina carriers have been developed to complete the oxidation of carbon monoxide and unburned hydrocarbons in gasoline engine exhaust. Platinum and/or palladium dispersed as very fine particles on pellets or greens of alumina have served as oxidation catalysts. These catalysts have proven most effective when there is an excess of oxygen in the exhaust gas resulting when the engine is operating in a fuel-lean or excess-air mode. The catalytic conversion of nitrogen oxides to nitrogen is a chemical reduction-type reaction which is most favorably carried out in an oxygen-deficient environment than is the antithesis of a favorable oxidation reaction medium. Under suitable engine operating conditions, a three-way catalyst promotes simultaneously the oxidation of carbon monoxide to carbon dioxide, the oxidation of unburned hydrocarbons to carbon dioxide and water and the reduction of nitrogen oxides to nitrogen. The three-way catalyst practice represents the current state of the art in gasoline-fueled engine exhaust treatment. The problem has been discovered with natural gas fueled engines is that when operated with a three-way catalyst in accordance with gasoline-fueled engine practices, unburned methane passes unoxidized through the exhaust system into the atmosphere. Although methane is not poisonous and it is not a reactive hydrocarbon in the sense that it promotes ozone formation at low altitudes, it is a greenhouse effect gas. It remains in the atmosphere and has many times the atmospheric heat-reflecting aspects of carbon dioxide.
Methane is not readily oxidized in an oxygen-rich exhaust gas over the traditional noble metal catalyst. These catalyst do not become “active” to oxidize methane until heated to very high temperatures (i.e. 600° C. or higher) which the exhaust gases usually do not attain. Thus, while the engine emissions with methane fuel are favorable compared to gasoline-fueled engines, there remains the problem of preventing unburned methane from escaping the engine's exhaust system into the atmosphere. Heretofore, there has been little effort in monitoring and controlling the emissions of methane from such natural gas fueled engines.
Methane emissions are monitored by the EPA and the Texas Commission on Environmental Quality (“TCEQ”). Industrial-grade engines that are being used in the oil and gas fields are designed to operate in austere conditions and even continue to operate in the event that multiple cylinders have suffered catastrophic failures. In doing so, there will be a significant increase in the amount of methane present in the engine exhaust. An engine can run continually in conditions such as this and cause the owner or operator to be responsible for the increased emissions and any fine deemed appropriate by the EPA or the TCEQ. As such, a need has developed so as to provide a device that can prevent this type of lost revenue and enhance the technical capabilities of the mechanics and operators.
There has not yet been any attempt to solve the problems associated with excessive methane emissions in industrial natural gas engines because of the lapse in technology and the lack of enforcement of environmental standards. However, in recent years, it has become a high priority and is now monitored regularly by the EPA and the TCEQ.
One of the problems with attempting to sense methane emissions from internal combustion engines is that water vapor is always present in the exhaust stream of a natural-gas fueled engine and rapidly condenses to form droplets as the engine exhaust cools. In any methane sensing system, the results and the detection can be compromised by contact with these water droplets or as a result of excess water within the exhaust gas being sampled. As such, a need has developed so as to provide a methane sensor which effectively avoids the problems associated with water vapor in the exhaust stream.
In the past, various patents have issued relating to the measurement of methane concentrations. For example, U.S. Pat. No. 4,329,870, issued on May 18, 1982 to D. E. Farmer, shows a methane monitor sensing system. This methane monitor has at least one removable and replaceable sensor interchangeably inserted into a receptacle located on the outside wall of the monitor.
U.S. Pat. No. 4,591,414, issued on May 27, 1986 to Zaromb et al., describes a method of determining methane and an electrochemical sensor therefor. An electrochemical cell is used for the detection and measurement of methane in a gas by the oxidation of methane electrochemically at a working electrode and a nonaqueous electrolyte at a voltage of about 1.4 volts versus the reversible hydrogen electrode potential in the same electrolyte. A measurement of the electrical signal resulting from the electrochemical oxidation is obtained.
U.S. Pat. No. 4,567,366, issued on Jan. 28, 1986 to A. Shinohara, discloses a method and apparatus for measuring methane concentration in a gas. This method and apparatus comprises a transmitting light having at least one wavelength band selected from a band of 1.6 μm and a band of 1.3 μm through an optical fiber having a small transmission loss in the wavelength bands to a measuring cell wherein ambient gas comes in and out. Light is absorbed in at least the characteristic absorption wavelength of methane gas. The light is transmitted through an optical fiber having a small transmission loss. The light is separated into at least one light having the methane gas absorption wavelength. At least one light has another reference wavelength so as to allow for the determination of the intensity ratio of the light having the wavelength to be measured to light having the reference wavelength. Methane gas concentration is calculated in the measuring cell from the so-determined intensity ratio.
U.S. Pat. No. 4,871,916, issued on Oct. 3, 1989 the J. C. Scott, teaches the sensing of methane using a spectroscopic method. This spectroscopic method senses the presence of methane in atmosphere. Atmospheric light emitted by a neodymium laser is utilized so as to have a fluorescent linewidth which embraces at least one significant absorption line of the band of methane.
U.S. Pat. No. 5,311,851, issued on May 17, 1994 to H. W. Wright Jr., provides a methane monitor and engine shutdown system. The system is used to detect methane gas at oil well and natural gas well sites. The system generates a warning signal when a first lower concentration of methane gas is detected and generates a second signal when a higher, more dangerous, level of methane gas is detected. The methane monitoring control and sensor device is mounted within the environment of an internal combustion engine and is used to detect the concentration levels of methane gas and generate two signals. A first signal generates a warning and a second signal will effect engine shutdown by means of a compressed air-operated valve closing the air intake to the engine.
U.S. Pat. No. 5,767,388, issued on Jun. 16, 1998 to Fleischer et al., discloses a methane sensor and method for operating such a sensor. The sensor has a temperature in a range of 700° to 850° C. for detecting methane and an oxygen-sensitive semiconducting metal oxide.
U.S. Pat. No. 5,131,224 provides a method for reducing methane exhaust emissions from natural gas fueled engines. This method allows the operating of the engine with an air-fuel ratio within a range that includes the stoichiometric air-fuel ratio and extends to the fuel-rich side. The system employs in combination with the engine a platinum or platinum and palladium metal catalyst for treatment of the engine and exhaust gases.
U.S. Pat. No. 5,969,623, issued on Oct. 19, 1999 to Fleury et al., describes a gas alarm that includes a methane sensor coupled to a processor for independently sensing methane levels such that an alarm is activated when the methane levels are above a predefined threshold.
It is an object of the present invention to provide a methane gas detection system that effectively detects methane concentrations as emitted from an internal combustion engine.
It is another object of the present invention provide a method and apparatus that enhances the technical capability of mechanics and operators.
It is another object of the present invention provide a method and apparatus that provides data to the mechanics and operators.
It is still a further object of the present invention provide a methane detection method and apparatus that helps to avoid fines by government authorities.
It is still another object of the present invention provide a methane detection apparatus and method that prevents lost revenue.
It is still a further object of the present invention provide a method and apparatus for detecting methane emissions that enhances environmental quality.
It is another object of the present invention to provide a methane detection apparatus and method which is extremely durable.
It is another object of the present invention to provide a methane detection apparatus and method that can be of a relatively small size.
It is still another object of the present invention to provide a methane detection apparatus and method that is reliable in the presence of a corrosive gas, such as hydrogen sulfide.
It is still another object of the present invention to provide a methane detection apparatus and method that is extremely accurate and reliable.
It is a further object of the present invention to provide a methane detection apparatus and method which allows the levels of methane to be easily observed.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.